Announcement

Collapse
No announcement yet.

Senft "Poppin" ENGINE

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    The sexy cylinder is under way. Now I have to make a 5/8" expanding mandrel to mount it on so I can turn the radius on the big end.

    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

    Comment


    • #17
      Here we have the sexy cylinder finished except for the tapped holes in each end. It is still mounted on the expanding mandrel in the picture.
      Brian Rupnow
      Design engineer
      Barrie, Ontario, Canada

      Comment


      • #18
        This morning yielded a cylinder head. Nothing very fancy compared to some cylinder heads I have made, but it should get the job done. How do you like my cylinder?
        Brian Rupnow
        Design engineer
        Barrie, Ontario, Canada

        Comment


        • #19
          Looks very good, looks more like a commercial model aero engine cylinder!
          CNC machines only go through the motions.

          Ideas expressed may be mine, or from anyone else in the universe.
          Not responsible for clerical errors. Or those made by lay people either.
          Number formats and units may be chosen at random depending on what day it is.
          I reserve the right to use a number system with any integer base without prior notice.
          Generalizations are understood to be "often" true, but not true in every case.

          Comment


          • #20
            Yes it looks very well proportioned, and as in form follows function, the hot end has more surface area for greater heat dissipation.

            The sliding valve that closes off the flame port, I had assumed it would ride in a slot to keep it aligned???
            Also what keeps this valve tensioned against the cylinder in order to keep it from leaking?

            I'm sure if I wait a few hours my questions will be answered with a video of a running engine.
            Home, down in the valley behind the Red Angus
            Bad Decisions Make Good Stories​

            Location: British Columbia

            Comment


            • #21
              Willy--That slide that blocks off the port is on the end of a cam operated lever. It is only 0.002" thick, so theory is that the suction from the piston will pull it into place to fully block the port.
              Brian Rupnow
              Design engineer
              Barrie, Ontario, Canada

              Comment


              • #22
                Love the cylinder. Looks like a ray gun from the cover of astounding.

                Comment


                • #23
                  Today I made flywheels. I can't even imagine it, but that's a full 8 hours of my time. These flywheels are somewhat unique, because the hubs will be made as separate pieces. Maybe I'll make them tomorrow.
                  Brian Rupnow
                  Design engineer
                  Barrie, Ontario, Canada

                  Comment


                  • #24
                    Two words.

                    Pretty!!
                    At the end of the project, there is a profound difference between spare parts and left over parts.

                    Location: SF East Bay.

                    Comment


                    • #25
                      Not a great deal done today, as I had a few hours of "real" work. I did however manage a pair of flywheel hubs and their accompanying nuts. (I cheated on the nuts---took a pair from my tool-chest and thinned them down on the lathe.) I have never seen flywheels made this way before, but it seems to work okay.
                      Brian Rupnow
                      Design engineer
                      Barrie, Ontario, Canada

                      Comment


                      • #26
                        Not a criticism, but an observation. Nothing shows up worse on a model engine than wobbling flywheels. When I make flywheels I generally leave a bit extra on the width and the diameter so that I can mount the finished flywheel on the correct size of arbor and give them a final "dressing" on the lathe to ensure that they are not wobbly as they revolve. Making flywheels with separate hubs that are not in any way "keyed" to the flywheel doubles the effort required to have the flywheels run true on the finished engine.
                        Brian Rupnow
                        Design engineer
                        Barrie, Ontario, Canada

                        Comment


                        • #27
                          Originally posted by brian Rupnow View Post
                          Not a criticism, but an observation. Nothing shows up worse on a model engine than wobbling flywheels. When I make flywheels I generally leave a bit extra on the width and the diameter so that I can mount the finished flywheel on the correct size of arbor and give them a final "dressing" on the lathe to ensure that they are not wobbly as they revolve. Making flywheels with separate hubs that are not in any way "keyed" to the flywheel doubles the effort required to have the flywheels run true on the finished engine.
                          If the flywheels are dimensionally accurate they should run true. What you are correcting for is a off center bore or something similar. Truing them up as described make them "appear" to be runout free but they will no longer be dimensionally accurate and thus be out of balance. For example, say the flywheel is 1/2 inch thick and wobbles, you true it up, its no longer half inch thick all the way around, some sections are thinner and thus not balanced. Kind of the same principle as mounting something off center in a 4 jaw chuck, the turned diameter will run true but its still off center in the jaws and out of balance. Two piece assemblies with a hub will run true if machined well, they do it every day with pulleys and taper lock bushings for example.

                          Of course a bent shaft out of alignment crank will cause the same effect.
                          Last edited by Sparky_NY; 03-14-2018, 11:52 PM.

                          Comment


                          • #28
                            It should be balanced if trued up.... at least if it "wobbles" sideways. To stop the wobble you will take material off until both sides run true, and the thing will still be in balance, just thinner.

                            If the wheel "runs out" radially, then if it is made with a hollow center, as usually done.... then if you just true the OD it will be out of balance unless you also true up the ID of the hollowed out portions. If you do that, it will be lighter, but it will be in balance.

                            Brian knows that stuff, he'll get it right.
                            CNC machines only go through the motions.

                            Ideas expressed may be mine, or from anyone else in the universe.
                            Not responsible for clerical errors. Or those made by lay people either.
                            Number formats and units may be chosen at random depending on what day it is.
                            I reserve the right to use a number system with any integer base without prior notice.
                            Generalizations are understood to be "often" true, but not true in every case.

                            Comment


                            • #29
                              Originally posted by J Tiers View Post
                              It should be balanced if trued up.... at least if it "wobbles" sideways. To stop the wobble you will take material off until both sides run true, and the thing will still be in balance, just thinner.

                              If the wheel "runs out" radially, then if it is made with a hollow center, as usually done.... then if you just true the OD it will be out of balance unless you also true up the ID of the hollowed out portions. If you do that, it will be lighter, but it will be in balance.

                              Brian knows that stuff, he'll get it right.
                              I was just going by the process as he described it. He made no mention of balance. or truing up the ID after doing the OD, thus why I made the post.

                              Comment


                              • #30
                                I can't swear to this, but my plan to address the flywheel issue is this. I will probably build the cam and cam washer and install them on one of the flywheels, then mix up a batch of J.B. Weld, coat the hubs with it, insert hubs into flywheels put cam and cam washer on one of the flywheels, then run the nuts down tight, and clean up any squeezed out mess. This should make each flywheel assembly a "composite unit". Then after 24 hours I will mount each assembly on a 3/16" arbor, tighten in place with the set-screws in the hubs, then true each flywheel individually. I am not concerned about balance here, just visual "flywheel wobble".
                                Brian Rupnow
                                Design engineer
                                Barrie, Ontario, Canada

                                Comment

                                Working...
                                X